Question measuring duration @ .050

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W2-1969Dart

W2-1969Dart

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Degreeing in my first camshaft not sure if the cam is ground wrong or I'm doing it wrong. Intake CL 108.25 and Exhaust CL 112 which are good , Lift 372 thats ok but when I check duration I get [email protected]ure Setting dial indicator to zero at base of cam rotating to .050 on the dial read the degree wheel 7 rotate past max lift to within .050 of base read degree wheel 43 add the two together plus 180 =230 any ideas cam is P4120655
 
Are you reading the dial indicator off the cam lobe or the lifter
 
Are you sure the degree wheel is set at 0 at a true TDC That cam should have [email protected] And if installed at 108* the intake readings at .050 would be 18* and 54*
 
Make sure that you have the degree wheel properly set, or compensate for the offset if any. It's easy to get confused.
 
Going to put the isky 555 cam back in that has very similar specs and check it. This is driving me crazy, the cam must be ground wrong
 
Make sure the end of your probe isn't changing position on the lifter
 
I tried to Google this, are these specs at the LIFTER or the VALVE?
 
Well. You are missing 11* on each side vs what you should be seeing...
 
i used to run that cam , and measured it with success. the only way i can figure it out from your measurements is this. you are 7* past and 43* before on a 180* spread. which means the CAM duration is 180*-7*-43*= 130 CAM degrees. because you measured on the cam , for crank degrees multiply by 2 , which gives 260* duration at .050 . although this seems a little high for the 557 mopar, keep in mind that the .050 measurement is for .050 NET VALVE LIFT. that means that you should be looking for (.050 +lash divided by 1.5) at the cam. this means you should check on the cam at (.050+ .028 / 1.5 )= .052 on the intake and ( .050+ .032 / 1.5 )= .055 on the exhaust. these checking points should bring back duration in line with the specs. for my cam, my measurements gave low to mid 250`s duration at 050 but advertised ( .006 at the VALVE) gave me a low to mid 280 number , which is lower than the specs. hope i didnt confuse you , any questions just ask. after all , this is just simple maths.
 
According to the MP "Small Block "A" Engines" book, this:

MP purple cams are sold by ADVERTISED duration and NOT "at 50"

Quoting page 186

"To calculate the duration at fifty number for a PRODUCTION camshaft, you multiply the advertised duration by .777. For a Mopar Performance Parts camshaft you multiply the advertised duration by .850."

SO THE SPECS IN THE CHART are an "advertised" number NOT duration "at .050"
 
7e5hangten360 said:
....................keep in mind that the .050 measurement is for .050 NET VALVE LIFT..
Click to expand...

Can you justify that statement. I've been looking for this spec. I could not find it in the MP book, all it says is ".050 lift" or "lift at 50".

The Comp Cams website says LIFT AT THE TAPPET
 
I have resolved my problems. What I did was I used a roller lifter :eek:ops:to gain some height for the dial indicator that would explain the 11 degrees, not thinking about the surface area. rechecked with PROPER LIFTER Intake duration 255 Exhaust 254 Intake CL 108.5 Exhaust CL 113 lobe seperation 110.75 Intake lift .557 Exhaust lift .555 thanks to everybody for trying to help sorry for wasting your time Brent
 
67Dart273 said:
Can you justify that statement. I've been looking for this spec. I could not find it in the MP book, all it says is ".050 lift" or "lift at 50".

The Comp Cams website says LIFT AT THE TAPPET
Click to expand...

The following timing is taken at .050" lifter rise and gives a more accurate determination of camshaft position.This info was is the timing chart from Isky but very close to the MP. the link is below.
http://www.iskycams.com/Wcc422c9a48168.htm

thanks again for everybody help
 
Yeh, I was asking 7e5, who was talking about "valve lift."
 
67dart273 : to the best of my knowledge, here it is : when measuring a hydraulic, advertised duration should be at .006 at the valve ( .006 at the cam should be very close). for duration at .050 it should be for 050 at the valve (.050 net valve lift ) , which should give .033 at the cam (.050/1.5). for a solid or a roller, as mentionned before, lash should be acounted for WHEN MEASURING AT THE CAM , because it is .050 AT THE VALVE ( .050 NET valve lift) for 050 duration and .006 AT THE VALVE for advertised. which means the checking point for advertised duration at the cam should be ( .006 +lash/1.5) and the checking point at the cam for 050 duration should be ( .050 +lash/1.5) . i found out that is the only way all these calculations make sense. either a hydraulic , solid or roller , using advertised or at 050 durations, it is always net valve lift that is used. measure one for yourself and you will see.
 
the number of cards I've seen that have timing event for at valve are few. When you add mechanical items, varying rocker ratios, bad tappet angles you only confuse/muddy the measurement

Almost every one for an ohv, pushrod, rocker arm style are at the tappet.

Go look at any sb, bb, hyd, solid or roller cam card from manufacturers and I'd doubt you'll find a card at the valve. It's not the norm, nor std practice.
 
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